Digester



`(No Model.)

S; SMITPL DIGI-3 STER.

No. 443,922. Patented Deo. so, 1890,.

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WTNESSs:

ma Ncnms Finns co., Primo-Limo., wAsmNcn'oN, D1 c.

, IAUNITED `STATES. ATENT .SIDNEY SMITH, OF CAMBRIDGE, MASSACHUSETTS.

DIGSTER.

` SPECIFICATION forming part of Letters Patent No. 443,922, datedDecember 30, 1890.

Application filed April 9, 1889. Serial No. 306,589. (No model.)

To all whom t may concern:

Be it known that I, SIDNEY SMITH, of Cambridge, in the county ofMiddlesex and State of Massachusetts, have invented certain new anduseful Improvements in Digesters, of which the following is aspecification.

This invention relates to steam-boilers composed of two shells, oneinclosed within another of a larger size, so that heat may be applied tothe space between the boilers for the purpose of acting on substancescontained within the smaller inside boiler. The invention relatesparticularly to such boilers as are used for t-he preparation of purevegetable fiber from wood and other substances from which pulp isproduced for paper-manufacture and analogous uses.

My invention has for its object, first, the construction of the two saidboilers in such a manner that the inner one is completely enveloped bythe outer one, so as to leave a continuous connected space all around,access to the inner shellbeingpossible onlythrough that of the outerboiler, and, second, the improvement of such boilers so that the innerboiler can be readily separated from the outer whenever it is desirableto make a critical examination of both shells for defects arising fromacid leaking through, or from any cause whatever, and can be repaired inthe cheapest, best, and quickest manner. The continuous space betweenthe two shells is especially important in paper-manufacture where thecoating or lining of the inner shell, to protect the shell from theaction of the acid liquor, is produced by exterior heat from such aspace, which precipitates upon the inner shell a firm durableincrustation.

The process of the formation of the incrustation when a bisulphiteliquor is employed is believed to be as follows: The sulphurous acid isexpelled from the bisulphite liquor by heat, producing monosulphite ofcalcium and free sulphurous-acid gas, thus CaH2(SO3)2-lheat=OaSO3+H2O+SO2- The nionosnlphite of calcium adheres wherever itcomes in contact with a metallic surface which is heated from theopposite side. The other product of decomposition, which issulphurous-acid gas, either bubbles up through the solution collectingin the upper part of the digester or attacks the gums and othersubstances which till the cells of the cellulose of the wood chips. Inorder that Stich a precipitated lining shall be even and continuous, itis necessary that the surface of the inner shell shall be perfectlysmooth, with no projecting rivet or bolt heads or other protuberances,for the lining tends to scale off from projecting boltheads, and isformed most perfectly where the surface to be coated is very smooth andregular. I provide for such an even surface by count-ersinking allrivet-heads in the inner boiler, and by joining the plates bydovetailing and iilling the small spaces left with lead or any materialwhich is not attacked by the contents of the digester. Both the innerand outer boilers are provided with suitable man-holes for theintroduction of stock, and also with all necessary connections, gages,

thermometers, duc., required for the purpose of accurately determiningthe condition of the inner contents. To facilitate the removal of theinner boiler, I provide the same with wheels at suitable intervals alongits outer circumference. These wheels run upon and are guided bysuitable rails placed longitudinally along the inner surface of theoutside boiler.

The outer boiler is provided with a removable head, so that by means ofthe wheels and rails described above the inner boiler can be run out andcompletely separated from the outer boiler. The inner boiler can be4again run back into position within the outer boiler and the head of theouter boiler screwed on, producing a true jacketed boiler, as describedpreviously. To firmly secure the inner boiler in place within the outerboiler or shell, I

IOO

longitudinal section of aportion of the inner shell. Fig. 4 represents alongitudinal section of another portion of the inner shell.

The same letters of reference indicate the same parts in all thefigures.

In the drawings, a represents the outer or inelosing` shell, and Z1represents the inner shell or digester proper. 'lhe outer shell isprovided with a detachable head c, and may be supported in any suitableWay. I have here shown trunnions d d on theheads of the outer shellfitted in bearings e c., so that the outer shell with the inner shelltherein contained can be rotated. The pipe fthat admits steam to thespace between the inner and outer shells passes through one of saidtrunnions.

g g represent 'the wheels which are applied to the inner shell, 'saidwheels being arranged to run on tracks h h, attached to or formed on theinner surface of the outer shell and extending lengthwise of the latter.

i' il represent the screws, which are engaged with tapped sockets ornuts in or affixed to the outer shell, and bear at their inner ends onplates jj, which rest on the surface of the inner shell. Said screwswhen turned inwardly press the plates against the inner shell and causesaid plates to act as clamps or brakes, preventing independent movementof the inner shell.

fifi represent lock-nuts on the screws t' i, said nuts being arranged tobear on the outer surface of the outer shell.

m m represent the coinciding man-holes, with Which the two shells a andb are respeotively provided.

n represents the pipe which conducts the acid liquor into the innershell when the latter is empty or before it is charged, for the purposeof forming the protecting coat or incrustation. Said pipe is arranged sothat the streams of liquor forced through its numerous perforations willstrike all portions of the inner surface of the inner shell or digester.rlhe inner shell may be rotated, if desired, during the admission of`the acid liquor through the pipe n, or the pipe may be rotated to morethoroughly distribute the liquor over the surface of the inner shell. Ifind that by thus Washing the inner surface of the digester with theacid liquor before charging the digester the protecting coat orincrustation is formed more quickly and thoroughly than when it isdeposited from the charge of liquor afterthe digester is filled orcharged.

The inner shell is made of plates 2 2 (see Fig. 3) of iron or steel, andto insure a perfectly smooth inner surface I countersink the heads ofthe rivets 3 3, that secure said plates, thus making said heads flushwith the inner surface of the digest-er. For the same purposeI prefer todoveta-il and slightly separate the adjacent ends of the plates 2 2 andsecure the same by means of extern al plates or bands 4, which areconnected by the rivets 3 to the plates 2. The dovetail space betweenthe ends of the plates within the band at is filled with a packing 5 oflead or other suitable acmresisting material Which is held in place bythe dovetail form of the ends of the plates, the inner surface of thelead packing being flush with the inner surface of the' digester.

It will be seen that by removing one of the heads of the outer shell andturning the screws e' outwardly the inner shell can'be readily removedfor inspection and repairs. The steam-space between the outer and innershells is conti1'1uous-or, in other Words, eX- tends over the entiresurface of the inner shell, so that all parts of said surface areexposed to the action of the steam or other heating medium admitted tosaid space, as already described.

In connection with the pipe 1t for spraying or Washing the inner surfaceof the digester with the acid liquor I prefer to employ a rota-ry brushh2, arranged to move over the 1nner surface of the digester and actafter the manner of a paint-brush in spreading and smoothly applying thesemi-Iiuid or plastic material left on the inner surface of the digesterby the partial evaporation of the aqueous portions of the acid liquor.Said brush is here shown as attached by arms bi3 b3 to the pipe n, andmaybe revolved over the inn er surface of the digester by the rotationof said pipe. The brush may be supported and operated in any othersuitable Way, or may be held stationary While the digester is rotated.It will be advisable to remove the brush as Well as the pipe n beforecharging the di gestel.

I claiml. The combination of a steam-tight inclosing-shell having aremovable end or head, means for detachably securing said head to thebody of the shell, and a removable herlnetioally-closed inner shellseparated from the outer shell by a continuous space, as set forth.

2. The hermetically-closcd inner shell or digester having wheels,combined with the steam-tight outer shell supporting said Wheels andhavinga detachably-secured end orhead to permit the removal of the innershell, as set forth.

3. The combination of the hermeticallyf closed inner shell or digesterhaving the Wheels and the steam-tight outer shell having longitudinaltracks on Which said wheels are adapted to run, and adetachabl y-secured end or head, as set forth.

4. In a digester, the ksteam-tight inclosingshell having a removable endor head, longitudinal tracks, and a man-hole, combined with thehermetically-elosed removable inner shell having wheels adapted to runon said tracks and a manhole connecting with the man-hole of the outershell, and clamping devices or brakes interposed between the inner andouter shells, whereby the inner shell may be locked Within the outershell, as set forth.

5. The combination, substantially as here- TOO inhefore sefforth, of ziboiler or digesier, :i heet to the Surface of seid digesier,substanperforatecl pipe or pipes within the same nrtinlly as seiI forth.

rangedto directstrea-ms of aeicl liquoraga-inst In testimony whereof Ihave signed my the inner surface of JLhe cligester, and means naine tolthis specification, in the presence of I5 for externally heating thedigester. two subscribing witnesses, this 2d day of 6. The combination,with i digester and a April, A. D. ISSS). pipe for spraying or Washingthe inner surface thereof with acid liquor, of u brush whereby thedeposit formed on the inner surface of said digester by the acid liquormay he uniformly spread, and means for applying l SIDNEY SMITH.

Witnesses:

C. F. BROWN, A. D. HARRISON.

